Many people have written on the subject of converting beer kegs into kettles for homebrewing. I have no special insights to add to what others have written, but I did take a lot of pictures.

I found a decent stash of 50L kegs at a scrap metal dealer, Madison Steel in Kitchener, Ontario. Many of the kegs appeared to me to be in excellent condition. They all held pressure (be careful when testing this; I used a screwdriver, wrapped in a rag to block the stream of disgusting stale beer.) One had scarcely a scratch on it. I don’t know why they were scrapped. But I’m glad they were, because I got to buy them for their value as scrap, which isn’t very much (around CDN$15). I bought a whole bunch of them, which will eventually all be converted into kettles for myself and some brewing friends.

Removing the Top

So, here’s your basic, unmodified beer keg. This is the first one I bought, and it isn’t quite as nice-looking as some that came later:

The first, and most difficult step is to get the top off. Some people have suggested using a “sawsall”, and a lot of sweat. I happen to have a coworker who has a plasma cutter. A plasma cutter makes the job quite easy. The hard part is keeping a steady hand and following the line you marked on the lid, which is hard to see with the welding glasses on. I have no pictures of that process, but here’s the finished result, and a close-up of the cut the plasma cutter makes:

We did a little test of the cutter inside the circle we intended to cut, just to get a feel for how the cutter would work. Here’s the one new insight on keg-conversion that I can give. When we started to make that first hole with the cutter, we were suddenly blasted with a spray of disgusting stale beer. When we stopped laughing, we tried to figure out what happened. The beer, after all, is at the bottom of the keg, and we were cutting on the top. Eventually we figured it out (but not before getting blasted with beer for a second time). And here is the advice: when making the first hole with the plasma cutter, make sure the valve on the keg is closed. I had the valve slightly ajar from when I released the pressure earlier. Now, a plasma cutter has a stream of compressed air, with a plasma arc. The plasma arc melts the metal, and the compressed air then blows the molten metal through the other side of the cut. Normally, a keg is completely sealed, and your first puncture will actually pressurize the inside of the keg. Since our keg valve was slightly open, what happened was the air pressure actually pushed beer up the keg’s dip-tube and out the valve opening, and all over us. Make sure the valve is closed, and you won’t get covered in beer.

Some people have suggested that the molten metal blown into the keg could weld itself to the bottom. In my experience, that didn’t happen. But as a precaution, you could fill the keg with an inch of water before cutting.

So, now we’ve got the opening cut into the top of the keg, and the valve and dip-tube removed:

Save the dip tube, it may come in handy someday. I held onto them for years, until I realized I could use one as the mechanical shield around a glass sight gauge.

The inside of the keg is a little bit yucky. Breweries clean them with a high-pressure blast of powerful chemicals. We have to rely on elbow grease. At least with the top cut off, it’s possible. I used some PBW (Powder Brewery Wash) from Paddock Wood, it’s quite good. (Paddock Wood is no longer running their web-store, they’ve converted into a microbrewery.)

The plasma cutter actually leaves quite a nasty jagged edge on the inside of the cut. It has to be ground off. I used an angle grinder. It makes a terrible racket, wear hearing protection.

All that being said, this guy has a pretty fine approach, which I’ll probably try in the future.

Plumbing the Keg

So, now we’ve got a basic 50L stainless steel kettle, for a fraction of what it would cost to buy one. But for brewing use, we need some more work. It needs some plumbing. You may need to decide what use the keg will be put to at this point. Typically, it will be a hot-liquor tank, mash tun, or boiling kettle. So far, I’ve made an HLT and a boiling kettle. The required plumbing in each case will be different, but for starters I install at least one 1/2″ pipe-coupling, near the bottom of the side wall. That basic fitting can be basis for any of the three applications. In some kegs, I installed two pipe couplings, 90° apart. The second coupling can accommodate a thermometer and/or sight gauge.

I obtained stainless pipe-couplings at the Desco Plumbing and Heating Supply store in Cambridge, Ontario. The pipe-coupling should be welded to the side of the keg, so that it is flush with the inside wall, and protruding on the outside. Installed that way, you have maximum flexibility in what you can do with the kettle. Plumbing can be installed on either the inside or outside, or both.

I drilled a hole in the side wall of the keg, just above the bottom, using a bimetal hole-saw. The hole made by the hole saw was slightly too small for the pipe-coupling to fit, so I had to enlarge the hole slightly with a Dremel and grinding stone. It was somewhat laborious, but the result was that the pipe-fitting could almost be press-fit into place.

At this point, it was necessary to enlist the aid of a professional welder. Welding stainless steel, especially thin stainless steel, is a skill that I will likely never have. But a professional welder can do it in moments, for only a small charge. Make sure the welder understands this is a food-grade application and uses a suitable filler rod (containing no cadmium or anything nasty like that). The ultimate for this application would be a “sanitary” weld, where both sides of the weld are blanketed with inert gas during the welding process, and the inside is ground smooth and polished. But that’s probably overkill, unless you’re going to use the keg as a fermenter. But you should at least try to have it welded both inside and out. If you only weld one side, the other side will be left looking nasty and the gap between the keg wall and the pipe coupling will be a trap for gunk.

I took my kegs and pipe-couplings to Grand Valley Specialty Welding in Kitchener. He didn’t do sanitary welds, but he did weld both inside and out, and it wasn’t too expensive.

At this point, you have a basic “universal” kettle. Your application will determine what fittings you install on the pipe-coupling. 1/2″ pipe fittings are commonly available, at least in brass. Stainless steel fittings are much more expensive and harder to find. If you use brass (I did), see this link for how to “pickle” the brass to remove lead from the surface.

Most applications are going to require some plumbing on both the inside and the outside. On the inside, because the pipe-coupling is a few inches higher than the concave bottom of the keg. You at least need a bit of tubing on the inside to reach to the centre of the bottom. And generally you’ll want a valve on the outside. You’ll typically also need a “close nipple”, to connect a female ball-valve to the female pipe-coupling on the keg. I got the nipples and full-port ball valves in stainless from Desco again. More expensive than brass, but not a deal breaker. Naturally, Teflon pipe-tape must be used to get a good seal.

Plumbing with Flare Fittings

For the inside plumbing, the first thing I put in is a 1/2″ MPT (male pipe thread) to 3/8″ MFL (male flare) adaptor. Flare connections can be easily assembled and disassembled, but pipe thread is a pain to deal with, so this adaptor is permanent.

In theory, you could use a conventional compression fitting, but they don’t really handle repeated assemble/disassembles very well.

Plumbing for a Hot Liquor Tank

The internal plumbing for the HLT is simple: just a drain tube. I wanted it to reach right to the bottom of the keg to suck out every last drop. It’s just a piece of 3/8″OD copper tubing, with a flare and flare nut at one end, and bent to the appropriate shape.

In addition, I have also added a glass sight gauge to my HLT, connected to a second 1/2″ pipe coupling installed 90° away from the drain fitting. This makes it easy to measure out specific volumes of water.

Plumbing for a Boiling Kettle

For the boiling kettle, I wanted a drain manifold on the inside. The idea is to avoid picking up the hops and trub when draining the kettle into the fermenter. I made a slotted drain mainfold out of 3/8″OD copper tubing. Then I bent the copper tubing into the desired shape: a ring around the centre of the bottom of the kettle.

A copper tee was used to bring a single branch off the ring manifold and up to the flare connection. The tee was actually a barbed tee for PEX tubing, but it happened to be almost exactly 3/8″ on the inside, close enough for solder to work.

I test fit it many times to make sure the manifold would lie close to the bottom of the kettle when installed on the flare fitting. When I was satisfied with the fit, I used my Dremel with a cut-off wheel to cut many small slots on the bottom side of the manifold.

The manifold goes around the center of the concave bottom, but not to the center. The theory of this was that after boiling the wort, I could whirlpool it, forming a mound of trub in the centre, and the manifold would drain clear wort from around the outside. In practice, the first time I used this system, the whole thing clogged up something awful with hop-pellet gunk, and I was forced to use a siphon instead. The next time I tried it, I used a mesh bag for the hop pellets. I used one of the nylon mesh bags sold at pet shops for aquarium filters.

Later, Whirlfloc tablets also clogged it up, forcing the siphon again. On the whole, it’s not been very successful.

Would you happen to know where I can find/purchase a 50L Keg in the US to use for my home kegerator? There’s a local brewer that is willing to fill it with my favorite beer however, they will not fill a “branded” keg. So I need a keg with a plain outer shell.

I’m loving all this great info on your website. Right now, I am working on a still and, as a boiler, I intend to use a 30 L keg that I got for free (free if the bill never arrives). The only problem is that I need to remove the rubber that covers all that steel and I the only idea I had until now is to burn it and I don’t think it would be a good idea because of all that smoke and pollution it would make (and it could weaken the steel). Have you got any idea of how to remove the rubber? Also, is any kind of lining used inside kegs that must be removed?

Burning it off is the easiest thing I can think of. But I don’t imagine it would be a pleasant fragrance. And the keg will be all blackened and nasty after. Maybe it would need to be sand-blasted or something after.

There is no inner lining in the kegs I’ve seen.

I don’t know much about still-building, but I do know that if you heat a sealed vessel, there is a considerable danger of an explosion. I guess a still would have a mash inside it, with lots of hard bits of grains and stuff that might clog your tubing. I don’t know much about stills, but one thing I do know is you need to be careful.

I saw above that you did not have a plan for the cutout and dip tube. I cut off the dip tube and welded 3 flat parts to the cutout and use it at a top. Amazingly, it fits better than a store bought pot lid…

can i please say to people this is a stupid idea, beer kegs are extremely dangerous things, the valve at the top has a thread inside it, which is under massive pressure, i work in a pub in england, a few years ago a worker at the pub down the road was changing a beer keg, it had been tampered with, as he was putting the tap on the keg, he had his head over the top of the valve, it shot out and blew half his brains onto the ceiling of the celler, BE CAREFUL.

I have to agree with Jon. “Close the valve” is super dangerous advice.

Prop open the valve, and deal with the spray. OR, knot up some old rags, and attach it to the keg spout so the spray is subdued. If you own a sankey tap, use it plus some scrap plastic tubing and vent into a bucket of water.

DO NOT CLOSE THE VALVE WHEN CUTTING THE KEG! The life you save may be your own, or someone nearby.

Now, to be perfectly clear, I was not suggesting that anybody cut into a pressurized keg. That would be foolish indeed.

I just want to warn people, if they cut with a plasma cutter, then the keg will repressurize just for a moment, with the compressed air from the plasma jet, when the plasma first pierces the keg. If you don’t want beer coming out the valve on you, make sure the valve is closed. Probably it would be a good idea, before starting with the plasma cutter, to use a regular twist drill to make a small hole somewhere else first, somewhere on the part of the keg that you’re going to be removing.

hi there. wondering if you had any of those kegs kicking around still? my dad dropped by madison steel for me today and they didn’t have any right now. if you had any extras i would gladly buy one from you. thanks for your articles, really appreciate your tips. craig. craigchurch@gmail.com

I own a metal fabricating shop in Texas and just bought a keg from a dude out of the back of his truck (I see nothing… I hear nothing). I got it back to my shop (the core for my shop is CNC plasma, been doing it for over 10 years)and pressed the ball down to equalize the pressure then started cutting (by hand not CNC). I left the valve shut so a didn’t get a shower of year old beer (Coors lite… yuk). Remember to vent the keg prior to cutting and you’ll have no worries!

Here is what you do to make sure you don’t kill yourself. Uses the back end of a screwdriver to push down the ball on the valve and vent the tank, if there is a lot of pressure and beer wedge the flat head of the screwdriver into the ball valve and set the keg on its side to allow all presure to vent. Then use the flat head of the screwdriver to pop the snap ring of the valve off. The valve and stem are threaded into the neck, use the screwdriver and a mallot to tap the valve counterclockwise and loosen the valve enough to remove it by hand. This way you can be sure that all the pressure is off the keg and drain out the old beer and add a little water if thats the way you want to go. If you are going to use a plasma cutter use a couple inches of water on the bottom to minimize spatter sticking to the bottom. Happy brewing.

For those without access to a plasma cutter, an angle grinder with a disc for cutting steel will also do the trick, albeit with a slightly messier cut. It can be cleaned up with a file, sandpaper, and patience.

thank you for the step by step. A friend and I are trying to start a small brewery in Quincy MA and I have been looking for kegs for our three tier system. Stumbled upon your site by accident, but very helpful! I liked the copper plumbing setup, was that for your Mash Tun ? email me. mfeirman@gmail.com

I had a stainless steel coupling welded to a keg. The welder assured me that he used stainless steel rods. He welded inside and outside the keg. The surface of the weld was left black and rough. I used “Bar Keepers Friend” cleaner, containing oxalic acid, to clean it up. I installed the nipple and valve, and put some water in the keg to test for leaks. Left the water in the keg overnight.
The next morning the inside weld was rusted. What do I do now. The welding job wasn’t cheap.

It’s possible, I guess, that the stainless weld did not have its “passivation” layer yet. Passivation is a thin layer of oxidized metal that forms on the surface of the metal and prevents further oxidation.

That is actually what makes stainless stainless. It is not true that stainless does not oxidize. It does, but it stops after the thin layer has formed. Apparently it’s the same with aluminum.

I gather stainless will passivate itself over time on exposure to oxygen. But there are chemical processes that can speed it up.

Thanks for your answer.
I’ll clean up the rust deposits with the same “Bar Keepers
Friend” and let the keg sit for a week or so, so that the surface can aquire this passivation layer.
If this doesn’t work, I may smooth the rough welding job with a “dremel”, and then polish the weld, and let sit for another week.
Mike.

As I said before, that’s a poor way to get a keg. It’s a good way to steal one, though. An even better way to steal one would be to snatch it from out behind a bar.

But it’s stealing either way. People doing that is the exact reason why many jurisdictions have keg registration laws now: they record your ID so they can find you if you don’t bring it back.

The problem in many places is that the scrap-metal value of a stainless steel keg is higher than the deposit.

The obvious solution would be to increase the deposit. But for some reason the brewer don’t want to do that. Presumably they’re concerned about losing business. I’m not sure why. It’s not the same thing as increasing the price of the beer. Whether the deposit is $40 or $400, the cost of a keg of beer is the same. I think everyone who’s mentally competent to buy a keg of beer understands that.

Just 3 notes. If you have the capability of tig welding stainless, you should not use threaded parts. You can use sanitary flanges with tri clamps (no need for teflon tape). It is much easier to clean and less surface area for micros to hide. Ball valves are a thing of the past when dealing with sanitary food processing. Butterfly valves are cheaper and much safer in regards to harboring bacteria. Last, using angle grinders on stainless leaves small particles of stainless inside the keg. If you want a truly sanitary system you will want to passivate the keg. You need to give it a high ph chemical bath for several hours at a temperature of 120 degrees. This will actually remove a small layer of steel and again create a much more sanitary environment. Consistency is key in brewing. Consistency means 0 bacteria. Sanitize, sanitize, sanitize.

I was just wondering if you are still converting kegs into boiling vessels and of so, how much do you charge? I am trying to get into full grain batch brewing and am in the market for two stainless boiling vessels right now.
Thanks

I have a huge selection of parts and components for making kegs or building your own bar. I bought in bulk from someone that installed bar equipment in bars and restaurants. I have hundreds of items such as regulators, tubing, electronic devices and sprayers, couplings, taps, just too much to mention and thousands of small parts also. Everything you would need to build your own bar. I just need a buyer. Will sell some of in or all of it. If anyone is interested or knows someone in the market who would be interested feel free to email me @ annette.wallace@hotmail .com. Located in Texas.